The present invention relates to a disk array device having plural disk drives and spare disk drives provided with the RAID (Residential Array of Independent Disks) function, in which data is copied from plural disk drives to one or plural spare disk drives in parallel, and a control method for the same.
Conventionally, a disk array device is provided with spare disk drives, in addition to employment of the RAID function, to improve the reliability thereof. In such a disk array device, when trouble has occurred in one of the disk drives constituting the RAID configuration, data is recovered from the other disk drives constituting the RAID configuration and is copied to the spare disk drives (correction copy), whereby the disk array device is recovered from a degenerate operation of the RAID function to a normal access state. However, since the disk array device sometimes enters the degenerate operation at the time of data recovery, there are problems in the reliability and performance thereof. Thus, the reliability is improved by analyzing an error history of the disk drives to predict the likelihood of a failure and by copying data in disk drives having a high likelihood of a failure to spare disk drives before a failure occurs (an operation called dynamic sparing).
However, recently, disk drives tend to have a larger capacity and are often used in a high load environment. Thus, the time required for the above-mentioned correction copy and dynamic sparing operations is increased.
Therefore, there is higher likelihood of occurrence of a multiple disk failure for the following reason. For example, it is likely that a trouble frequently occurs in a copy source disk drive and a READ operation cannot be continued during a copying operation for carrying out dynamic sparing. In this case, the disk drive is blocked, and a data recovery operation (correction copy) is carried out for a parity group (i.e., ECC (error correcting code) group) to which the disk drive belongs. However, it is likely that a problem, such as a partial sector fault or hard disk blocking, will occur in another disk drive in the identical parity group during this correction copy operation. If such a multiple disk failure occurs, data will be lost.